A Comprehensive Guide to Buying a Gemstone

While diamonds are beautiful, they are not for everyone. There’s been an a rising popularity in using other gemstones for engagement rings in recent years — but in fact, this isn’t a passing trend. While diamonds have been used in engagement rings since 1477 when Archduke Maximilian of Austria was first recorded to have commissioned one for his fiancée, other precious stones have long been used for betrothals.

Problem is, while there is a hard and fast certification process out there for diamonds, there isn’t one for gemstones and shopping for one can be a lot more challenging. Knowing how to measure quality and the proper outlets through which to source your gems is the best preparation you can give yourself. While there’s a world of precious and semi-precious stones out there, this is a guide for the most popular and a word of advice about some of the more recent trends.

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)

A GIA report is the safest bet

While the GIA doesn’t have a grading process for gemstones, they do issue reports. The report doesn’t plot out the stone as it does for diamonds, but will identify treatments that have been used on and accepted by (more on this later) the stone, whether it’s natural or not, and country of origin by request and an additional fee. Determining origin isn’t a perfect science, however, according to Heather Sandor of A and C Gem Trading Corporation, who has been in the business for over 30 years. “Sometimes you can send a stone to two different labs and get two different answers,” Sandor tells us, “Sometimes you can send it to the same lab, and get two different answers.”

Be familiar with the Mohs scale of mineral hardness

Aside from being a result of a very successful 1947 DeBeers campaign “A Diamond Is Forever,” there’s a practical reason why diamonds make great engagement ring stones. They are one of the hardest and hardiest minerals out there. They are a 10 on the Mohs scale of mineral hardness, which is the maximum grade. The Mohs scale is based on the ability of one type of mineral to cause a visible scratch on another, and diamonds are so strong, bits of them are embedded into saws and blades for industrial use.

But if you have your heart set on a stone of a different breed, you’ll want to know where your dream rock falls on this scale. Sapphires and rubies are great alternative choices as they are made of the same mineral, corundum, which scores a nine on hardness. Less ideal options are emeralds, which fall between 7.5 and eight on the scale, as they are more fragile. Another type of mineral that Sandor is quick to discourage us from considering is morganite, which also falls between 7.5 and eight on the Mohs scale. “It’s the [worst] choice Etsy ever put in peoples’ heads,” she said. “It’s a soft stone, so it’s not good for everyday use. An engagement ring should hold up to everyday use and generally it’s something you want to become an heirloom. Having a stone that’s soft [means] the facets will wear, it’s more susceptible to breakage or cleavage or scratching.”

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)

Know that a lot of gemstones are treated

Stone treatments vary from type to type of stone, and depending on how the stone was treated, that can greatly affect the price. The most expensive stones out there are natural, untreated stones. For sapphires and rubies, heat treatment happens for about 95% of all sapphires and can affect the price a bit, while chemical treatments can further degrade the price and the effects of treatment wear off over time. Emeralds are most commonly treated with oil (usually straight out of the source) and the ones from Colombia are often treated with resin.

So why are stones treated at all? Well, these treatments have a lot of aesthetic and sometimes structural benefits to a gem. Heat and chemical treatments for sapphires even out the color (though heat has a permanent effect and chemical does not) and improve clarity. It’s quite rare to find a sapphire that doesn’t need treating, which is why natural ones will fetch top-dollar.

Emeralds are treated for structural reasons because 99% of all natural emeralds have inclusions (if you ever see a perfect emerald that doesn’t cost your firstborn, run, because it’s for certain a fake). A common type of inclusions is fissures or feathers, and oil is often used to fill in the fractures, and can enhance the appearance of the stone.

In fact, when most emeralds are mined, they’re put into a barrel of oil. However, this doesn’t mean that the stone will be considered treated. “You could have a stone that when it’s been faceted, doesn’t have oil in it [even though] it had been put in a barrel with oil,” Sandor says, “The reason why it doesn’t have oil is because there was no surface for the oil to reach an inclusion. [It means] you have a finer material.” Treatment is only noted in a GIA report when it takes, otherwise, the stone is considered natural.

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)

Be wary of marketing trends

Aside from the somewhat impractical morganite becoming a trend thanks to Etsy, there have been an increasing number of less-than-quality stones growing popular due to clever marketing.

  • Despite what you see out there, color-changing sapphires aren’t a thing, though bi-color or parti-color sapphires are. However, there certainly are sapphires that appear to be different colors depending on the light, but this is only true for deeper hued stones. “What used to be the sapphires you couldn’t sell, the worst parts of the lot,” Sandor says, “they have been romanticized. They’re inexpensive, and if you can make something beautiful out of it, and someone wants it, then that’s wonderful, but don’t let them think that it’s more valuable [than it is].”

  • Sandor also warned of seeing something called a Padparadscha tourmaline, which doesn’t exist. Padparadscha sapphires are salmon pink and exceedingly rare, and therefore cost a premium. Salmon pink tourmalines are not nearly the same thing, though labeling them as “Padparadscha” allows vendors to mark up the price.

  • Jewelry designer Ashley Zhang also warned against the recent gray diamond trend, which have been marketed as everything from icy diamonds to salt-and-pepper diamonds. “A salt-and-pepper diamond just means that it has a lot of black inclusions, and it used to be considered industrial diamonds used for cutting things,” she tells us.

  • But ultimately, the goal is to end up with a ring you absolutely love. “If you’re buying something [that’s value is ] not measurable industry-wide, you have to know that it’s a personal choice, and it’s not a financial choice,” Zhang advises. “You’re not looking at it as an investment, you’re looking at is because that’s what you love, and that’s great.” But whether you’re buying a softer colored stone or a very included one, just know what the these are not the most durable choices, and may not be able to be passed down as heirlooms, or at least, “the way it looked when you received it.”

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)

Go to a trusted source

A lot of big box jewelry store carry subpar stones that are commercial grade, and may have been treated in questionable ways. A better investment is finding someone who can guarantee the quality backed with a real report.

“Go to a professional who is showing you concrete evidence that what they [say] have is what they [actually] have,” Zhang advises. Sandor says, “Look for somebody you trust. I would say always trust your gut. It doesn’t have to be [a] brick-and-mortar [store]. It could be online.”

For an industry outsider, a custom jeweler is your best source for good stones as many dealers only sell to jewelers.

And if you’re looking for a truly exceptional stone or if you’re looking for only ethically sourced stones, country of origin matters. One organization that’s working to build transparency in the jewelry business is Ethical Metalsmiths, which is a community of jewelers and dealers who are focused on responsible sourcing.

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)

Types of stones to consider


  • Made of corundom, it rates a nine on the Mohs scale of mineral hardness

  • Comes in a variety of colors, from the ubiquitous blue (and many shades of it) to rare peach to pink to yellow, even white

  • White isn’t a recommended color by Sandor and Zhang as a white sapphire doesn’t have fire (flashes of color) in the same way as diamonds

  • White sapphires also dull easily and require constant cleaning, but the same is not as true for color sapphires

  • 95% sapphires are treated with common treatments being heat (permanent effect, bring downs cost) or chemical (semi-permanent effect, impacts cost considerably)

  • Look for the strong flashes of the hue being reflected back to the eye, as this indicates a good cut and high quality stone

  • You want to see the facets

  • Clarity is ranked by VVS (very, very slight), VS (very slight), and I (included)

  • Watch out for lattice diffusion treatment process , which, according to the GIA, “uses heat and chemicals to diffuse an element into a gemstone to artificially change its color”


  • Made of corundom that possesses chromium oxide, which gives the gem a red tonality

  • Come in a range of reds from orangey red to a purplish-pink

  • Can also be treated with heat or by chemical to even out color and reduce the appearance of inclusions, and tend to have less clarity than sapphires

  • Are sometimes treated with glass, resin, or oil to fill fractures

  • Some of the most prized rubies are “pigeon’s blood red” rubies from Myanmar (Burma), which were embargoed in the US from 2003 to 2016

  • Large rubies are extremely rare, and so an untreated, two-carat ruby would fetch a higher price than a same-quality sapphire

  • Intensity of the red is the primary determining factor in the cost

(Photo: Kimberly Wang)

(Photo: Kimberly Wang)


  • Rank 7.5 to eight on the Mohs scale, so even though an enduringly popular option, it’s more high maintenance than rubies and sapphires

  • Does better in earrings or necklaces where a risk of fracture isn’t as great

  • Almost always contains inclusions, and are treated with oil and resin

  • Treatment is graded by the GIA as F1 (minor enhancement), which are very good; F2 (moderate enhancement), which are very common; and F3 (major enhancement), which are stones of the worst quality

  • Clarity, brightness, cut, and carat size all factor into the price, though color and clarity most of all

  • Mostly comes from Africa, South America, and Central Asia


  • Not quite as popular as the other three for gemstone engagement rings, but shouldn’t be overlooked

  • Ranks 6.5 to seven on the Mohs scale, should should be set in a protective setting, and should be worn with care

  • There are a wide variety of garnets, and each variety has a range of colors: red, orange, purple, green, yellow — you name it

  • Is much less in demand compared to the other three, and demand dictates price

  • Clarity of the stone depends on which variety of garnet

  • Demantoid and tsavorite garnets are rare in large sizes, whereas almandine garnets come in heavier carat weight, so is cheaper

  • Fun fact: Laura Ingalls Wilder’s engagement ring was a garnet